A mobile subscriber communication system may generally comprise a set of “mobile subscribers,” typically mobile subscribers are the endpoints of a communication path, and a set of “base stations,” typically stationary and the intermediaries by which a communication path to a mobile subscriber may be established or maintained. It is generally desirable in mobile subscriber communication systems to allow the rapid establishment of communication links between mobile subscribers and base stations, and rapid handoff between base stations, without errors and without inadvertently dropping the call or losing a communication link. This type of capability is generally accommodated by allowing the mobile subscriber to scan where scan means to go from listening to an associated base station to listening to a neighboring base station to determine which base station to hand off to when the need to handoff occurs. The mobile subscriber's ability to scan other base stations needs to be accommodated without affecting the mobile subscriber's ability to lose the current communication link.
Typically, an associated base station provides mobile subscribers scan opportunities for a mobile subscriber to establish a communication with other base stations and receive information relating to power estimation and signal quality estimation. Such scan opportunities are provided during times when the associated base station is not sending data or a slot assignment to the mobile subscriber. However, in order for such scan opportunities to be utilized properly, broadcast channels of the base stations surrounding the associated base station must be synchronized so that mobile subscriber scan opportunities coincide with broadcast channel transmissions. If the associated base station does not know when the mobile subscriber is scanning, the mobile subscriber may miss data or a slot assignment sent by its associated base station while it is scanning another base station. Missing data or a slot assignment wastes time slots and wastes communication bandwidth.
Therefore it would be advantageous to provide a synchronization system for base stations and mobile subscribers of a communication system whereby the mobile subscriber can scan other base stations other than the mobile subscriber's associated base station and still not miss data or slot assignments being sent to it by its associated base station. It would further be advantageous to provide a communication protocol enabling synchronization and control traffic functions, which is particularly suited to use in a time division multiple access (TDMA) environment.
It will be appreciated that for simplicity and clarity of illustration, elements shown in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements are exaggerated relative to each other. Further, where considered appropriate, reference numerals have been repeated among the figures to indicate identical elements.